1. Technical Field
The present invention relates to a controller for a stepper motor of N phase and N+1 phase energization type alternately using both N and N+1 phase energization.
2. Prior Art
Controllers for the stepper motor of N phase and N+1 phase energization type such as one-two phase energization, two-three phase energization or three-four phase energization have been proposed to execute both N and N+1 phase energization via a same pulse width, where N stands for an integer equal to or larger than 1. Thus, the initial pulse width for driving the stepper motor is always the same irrespective of whether N or N+1 phase energization is initially executed. However, since the energization current flowing through the stepper motor is variable depending on N phase and N+1 energization, the magnetism for rotating a rotor is also variable. Thus, using a constant pulse width irrespective of the initial phase energization either N or N+1, might cause uneveness of the follow-up characteristic of the rotor.